EMSUSD-3992 : New attribute for active Hydra renderer

lib/mayaUsd/nodes/sceneRenderSettings.cpp

@@ -170,6 +170,26 @@ bool setActiveSettingPath(const std::string& ufePath)
     return node->setActiveSettingsPath(ufePath);
 }
 
+std::string getCurrentRenderer()
+{
+    MayaUsd::UsdSettingsNode* node
+        = MayaUsd::UsdSceneSettingsManager::getNodeForNodeName(kRenderSettingsNodeName);
+    if (!node) {
+        return {};
+    }
+    return node->currentRenderer();
+}
+
+bool setCurrentRenderer(const std::string& rendererName)
+{
+    MayaUsd::UsdSettingsNode* node
+        = MayaUsd::UsdSceneSettingsManager::getNodeForNodeName(kRenderSettingsNodeName);
+    if (!node) {
+        return false;
+    }
+    return node->setCurrentRenderer(rendererName);
+}
+
 const PXR_NS::TfToken& externalCameraAttrName() { return kExternalCameraAttrName; }
 
 bool setRenderSettingsCamera(

lib/mayaUsd/nodes/sceneRenderSettings.h

@@ -48,6 +48,14 @@ MAYAUSD_CORE_PUBLIC std::string getActiveSettingPath();
 //! if the singleton node is unavailable or the plug write fails.
 MAYAUSD_CORE_PUBLIC bool setActiveSettingPath(const std::string& ufePath);
 
+//! Hydra renderer plugin name that drives USD Hydra rendering for the scene,
+//! or an empty string when none has been chosen.
+MAYAUSD_CORE_PUBLIC std::string getCurrentRenderer();
+
+//! Author the Hydra renderer plugin name on the render-settings singleton.
+//! Returns false if the singleton node is unavailable or the plug write fails.
+MAYAUSD_CORE_PUBLIC bool setCurrentRenderer(const std::string& rendererName);
+
 //! Name of the custom string attribute that records the UFE path of a camera
 //! that does not live on the same stage as the render-settings prim
 //! (e.g. a Maya native camera shape, or a camera in another USD stage).

lib/mayaUsd/nodes/usdSettingsNode.cpp

@@ -36,6 +36,7 @@ const MString UsdSettingsNode::typeName("UsdDefaultSettings");
 MObject UsdSettingsNode::serializedRootLayerAttr;
 MObject UsdSettingsNode::serializedSessionLayerAttr;
 MObject UsdSettingsNode::activeSettingsPathAttr;
+MObject UsdSettingsNode::currentRendererAttr;
 
 /* static */
 void* UsdSettingsNode::creator() { return new UsdSettingsNode(); }
@@ -84,6 +85,18 @@ MStatus UsdSettingsNode::initialize()
     status = addAttribute(activeSettingsPathAttr);
     CHECK_MSTATUS_AND_RETURN_IT(status);
 
+    // Hydra renderer plugin name persisted on the node to select which Hydra
+    // backend is used for USD rendering. Hidden/internal: reads/writes go
+    // through the typed accessors.
+    currentRendererAttr = typedAttrFn.create(
+        "currentRenderer", "crn", MFnData::kString, defaultStringDataObj, &status);
+    CHECK_MSTATUS_AND_RETURN_IT(status);
+    typedAttrFn.setStorable(true);
+    typedAttrFn.setHidden(true);
+    typedAttrFn.setInternal(true);
+    status = addAttribute(currentRendererAttr);
+    CHECK_MSTATUS_AND_RETURN_IT(status);
+
     return status;
 }
 
@@ -119,6 +132,19 @@ bool UsdSettingsNode::setActiveSettingsPath(const std::string& ufePath)
     return status == MS::kSuccess;
 }
 
+std::string UsdSettingsNode::currentRenderer() const
+{
+    MPlug plug(thisMObject(), currentRendererAttr);
+    return plug.asString().asChar();
+}
+
+bool UsdSettingsNode::setCurrentRenderer(const std::string& rendererName)
+{
+    MPlug   plug(thisMObject(), currentRendererAttr);
+    MStatus status = plug.setString(MString(rendererName.c_str()));
+    return status == MS::kSuccess;
+}
+
 void UsdSettingsNode::ensureStage() const
 {
     if (_stage) {

lib/mayaUsd/nodes/usdSettingsNode.h

@@ -61,6 +61,7 @@ class MAYAUSD_CORE_PUBLIC UsdSettingsNode
     static MObject serializedRootLayerAttr;
     static MObject serializedSessionLayerAttr;
     static MObject activeSettingsPathAttr;
+    static MObject currentRendererAttr;
 
     static void*   creator();
     static MStatus initialize();
@@ -85,6 +86,13 @@ class MAYAUSD_CORE_PUBLIC UsdSettingsNode
     //! false on plug-write failure.
     bool setActiveSettingsPath(const std::string& ufePath);
 
+    //! Hydra renderer plugin name that drives USD Hydra rendering for the
+    //! scene, or an empty string when no renderer has been chosen.
+    std::string currentRenderer() const;
+
+    //! Author the Hydra renderer plugin name. Returns false on plug-write failure.
+    bool setCurrentRenderer(const std::string& rendererName);
+
     // Serialization (called by UsdSceneSettingsManager scene callbacks)
     void serializeToAttributes();
     void deserializeFromAttributes();

lib/mayaUsd/python/wrapSceneRenderSettings.cpp

@@ -37,6 +37,10 @@ void wrapSceneRenderSettings()
         .staticmethod("getActiveRenderSettingsPath")
         .def("setActiveRenderSettingsPath", &MayaUsd::SceneRenderSettings::setActiveSettingPath)
         .staticmethod("setActiveRenderSettingsPath")
+        .def("getCurrentRenderer", &MayaUsd::SceneRenderSettings::getCurrentRenderer)
+        .staticmethod("getCurrentRenderer")
+        .def("setCurrentRenderer", &MayaUsd::SceneRenderSettings::setCurrentRenderer)
+        .staticmethod("setCurrentRenderer")
         .def(
             "externalCameraAttrName",
             +[]() { return MayaUsd::SceneRenderSettings::externalCameraAttrName().GetString(); })

test/lib/mayaUsd/nodes/testSceneRenderSettings.py

@@ -415,6 +415,64 @@ def testActiveSettingsPathResetOnFileNew(self):
             UsdDefaultRenderSettings.getActiveRenderSettingsPath(),
             defaultPath)
 
+    # ------------------------------------------------------------------
+    # Hydra renderer selection (currentRenderer)
+    # ------------------------------------------------------------------
+
+    def testCurrentRendererDefault(self):
+        '''Default currentRenderer is empty; no Hydra renderer is chosen yet.'''
+        nodeName = UsdDefaultRenderSettings.find()
+        self.assertEqual(UsdDefaultRenderSettings.getCurrentRenderer(), '')
+        self.assertEqual(
+            cmds.getAttr(nodeName + '.currentRenderer'), '')
+
+    def testCurrentRendererSetter(self):
+        '''Writing through the helper updates every read path.'''
+        rendererName = 'HdStormRendererPlugin'
+        self.assertTrue(
+            UsdDefaultRenderSettings.setCurrentRenderer(rendererName))
+
+        self.assertEqual(
+            UsdDefaultRenderSettings.getCurrentRenderer(), rendererName)
+        nodeName = UsdDefaultRenderSettings.find()
+        self.assertEqual(
+            cmds.getAttr(nodeName + '.currentRenderer'), rendererName)
+
+    def testCurrentRendererRoundTrip(self):
+        '''A custom currentRenderer survives a save/open cycle.'''
+        rendererName = 'SomeCustomRenderer'
+        self.assertTrue(
+            UsdDefaultRenderSettings.setCurrentRenderer(rendererName))
+
+        tmpDir = tempfile.mkdtemp(prefix='testSceneRenderSettings_')
+        try:
+            tmpFile = os.path.join(tmpDir, 'currentRendererRoundTrip.ma')
+            cmds.file(rename=tmpFile)
+            cmds.file(save=True, type='mayaAscii')
+            cmds.file(new=True, force=True)
+            cmds.file(tmpFile, open=True, force=True)
+
+            self.assertEqual(
+                UsdDefaultRenderSettings.getCurrentRenderer(),
+                rendererName)
+        finally:
+            cmds.file(new=True, force=True)
+            shutil.rmtree(tmpDir, ignore_errors=True)
+
+    def testCurrentRendererResetOnFileNew(self):
+        '''File > New restores the empty default value.'''
+        self.assertEqual(UsdDefaultRenderSettings.getCurrentRenderer(), '')
+
+        rendererName = 'TemporaryRenderer'
+        self.assertTrue(
+            UsdDefaultRenderSettings.setCurrentRenderer(rendererName))
+        self.assertEqual(
+            UsdDefaultRenderSettings.getCurrentRenderer(), rendererName)
+
+        cmds.file(new=True, force=True)
+
+        self.assertEqual(UsdDefaultRenderSettings.getCurrentRenderer(), '')
+
     # ------------------------------------------------------------------
     # Locked-node invariant
     # ------------------------------------------------------------------